The SENTRY-FOOT™ Flange-Type Foot Valve with Strainer

Energy-Saving Backflow Prevention and Priming Protection for Pumping Systems

The Flange-Type Foot Valve with Filter Screen (also known as a Sunction Valve, Well Bottom Valve, or Suction Strainer) is an essential, energy-saving valve installed at the submerged bottom end of a pump’s suction line. Its core function is to maintain liquid prime within the pump and pipeline by permitting flow in one direction only, preventing fluid from returning to the source when the pump stops.

🔑 Critical Features and Design Structure

The Foot Valve is comprised of the Valve Body, Bonnet, Disc, Seal Ring, and Gasket.

Component	Material (Typical)	Function
Valve Body/Disc	Ductile Iron (球墨铸铁)	Provides high strength and durability, especially for suction applications.
Seal Ring	NBR (Nitrile Butadiene Rubber)	Provides reliable sealing for tight shutoff against backflow.
Filter Screen (Strainer)	Stainless Steel / Galvanized Steel	Prevents large debris, trash, and foreign matter from entering the suction pipe and damaging the pump impeller.
Spring	Stainless Steel / Galvanized Steel	Ensures the disc closes quickly and positively when the pressure differential reverses (pump stops).
Disc Type	Lift Type (升降式) or Swing Type (旋启式)	Allows the disc to be opened by liquid pressure and rapidly closed by spring force/gravity and back pressure.

🎯 How the Foot Valve Works (The “Only In, No Out” Principle)

Pumping (Flow On): Liquid medium enters through the filter screen into the bonnet and then into the valve body. The pressure of the liquid acts on the disc, forcing it open and allowing the medium to flow freely into the pump suction line.
Pump Stop (Flow Off): When the fluid pressure within the valve body changes or disappears (i.e., the pump stops), the pressure from the pipeline acts on the closed side of the disc. The disc rapidly closes, preventing the liquid from flowing back into the source.
Energy Conservation: By restricting the liquid from returning to the source, the valve ensures the pump pipe remains full (primed). This saves energy by preventing the pump from having to lift the entire column of liquid again upon restart.

🛡️ Advantages and Applications

Filter Screen: The bonnet is equipped with multiple intake ports and a sturdy screen (Strainer) to minimize the ingress of debris, significantly reducing the chances of valve or pump clogging.
Low Friction Resistance: Advanced manufacturing processes ensure minimal friction resistance, contributing to a longer service life and better energy performance.
Convenience: Designed for easy installation, use, and inspection.
Versatility: Highly suitable as a pump accessory in industries including:
- Petrochemical & Chemical
- Textile & Dyeing
- Metallurgy & Mining
- Irrigation & Drainage

Important Note: Although equipped with a filter screen, this foot valve is generally designed for clean media. It is not recommended for media with excessive viscosity or high concentrations of large particulate matter, as these can still cause clogging over time.